Chewing gum generally contains gum base, an aqueous softener (such as corn syrup), a sweetening and bulking agent and flavor. Optional color and processing aid ingredients are also well known.
Chewing gum is generally prepared by mixing the gum base with the aqueous softening agent for three to five minutes, followed by the addition of solid sweetener and flavor. The gum is removed from the mixer, rolled and cut to the desired shape.
It is also well known that chewing gum has the tendency to get stale. Where the ambient relative humidity is less then the equilibrium relative humidity (ERH) of the composition, moisture is lost from the gum. After time, the gum becomes stale and brittle.
Various suggestions have been made for overcoming this problem. U.S. Pat. No. 4,166,134 to Witzel et al. ("Witzel") discloses a gum composition containing a humectant, which increases the ERH of the gum. Witzel discloses sugar alcohols as humectants, sorbitol being preferred. Also, Witzel states that the sugar alcohol should be about 2% to about 50% of the gum composition. Witzel also states that the humectant is to be effectively separated from the aqueous softener, and discloses a method wherein the sorbitol is added after first mixing the gum base and aqueous softener mixture with the sweetener. In fact, Example 8 of Witzel compares two gum compositions with identical ingredients, including 10% sorbitol, 17% corn syrup and 50% sugar. The Example 8 sample is produced with the sorbitol being added after the sugar, and in the control sample the sorbitol is mixed before the sugar is added. It was reported that after 72 hours of storage at 100.degree. F., the control samples had severe sweating and stuck together, while the Example 8 samples were easily separated, displaying good sweat resistance.
U.S. Pat. No. 3,632,358 to Enchandia et al. ("Enchandia") discloses a method of making chewing gum in which glycerin is added in an amount from about 0.1 to about 1% by weight of the gum. The glycerin is added after two-thirds of the sugar is mixed in. Glycerin is a liquid and has known humectant properties. In fact, the tendency of glycerin to attract water is so strong that it is often considered a desiccant.
Prior to the discovery of the present invention, applicants' assignee was making and selling a gum composition containing gum base, corn syrup, sugar and a small amount (less than about 1%) of sorbitol. The sorbitol was added to the gum composition after the sugar had been mixed with the gum base and corn syrup. This small amount of sorbitol was found to improve the long-term flexibility of the gum, although it did not significantly affect the ERH of the gum. However, the gum that was produced was found to be excessively soft and was difficult to wrap after a typical 24-hour cool down period between the rolling/scoring operation and the wrapping operation.